1. Field of the Invention
The present invention generally relates to an ultraviolet fluorescent lamp, and in particular to an ultraviolet fluorescent lamp used for suntanning.
2. Brief Description of Related Developments
Tanning is generally described as the darkening of one's skin through exposure to ultraviolet (UV) radiation. A person's skin reacts to UV radiation exposure. The reaction is generally dependent upon, for example, the amount of melanin pigment already in the skin naturally and the capability of the person's skin to produce additional melanin (facultative pigmentation).
Melanin is the dark pigment found in the retina, hair and skin, except for the palms of the hands, soles of the feet and lips. Without the protection afforded by the melanin pigment, a person's skin would bum when exposed to UV radiation. The skin includes naturally occurring melanin pigment and produces additional melanin. Melanin is produced by special cells called melanocytes, which are located deep within the outer layer of the skin. When the melanocytes are stimulated by ultraviolet light, they utilize the amino acid tyrosine to produce the melanin pigment. Since the melanin pigment is only able to absorb ultraviolet light of approximately 260-320 nanometers, UVB radiation is need to achieve melanin production. UVA radiation, which has a wavelength of approximately 320-400 nanometers, can promote the production of melanin, but only when there is enough photosensitizing material already in the skin to trigger a UVB reaction. With the presence of UVB, melanocytes are stimulated to divide, creating more pigment cells. During this time, the epidermis thickens to form additional protection, a condition referred to as acanthosis.
In the beginning stages of melanin production, the skin has very little melanin or radiation protection capabilities. As a result, UVA radiation is not blocked by melanin pigments and, due to its longer wavelength, penetrates the skin deeper than UVB, causing damage to the corium. Damage to this layer of the epidermis hastens aging and destruction of collagen and connective tissue. A UVA burn can cause serious damage because it is not felt due to its deep penetration.
Erythema is redness of the skin caused by increased blood flow to the capillaries. There are many causes and manifestations of erythema, one of the more frequent being photosensitivity. Photosensitivity is the reaction of the skin in response to the sun and tends to occur when an infection or a medication increases a person's sensitivity to ultraviolet radiation. Excessive sun exposure increases the risk for erythema multiforme.
Symptoms of Erythema multiforme include fever, itching of skin, a sudden outbreak of spots, bumps, and lesions, typically on knees, elbows, palms, hands, feet, and mouth.
In order for the pigmentation process to be effective, melanin granules must be oxidized or darkened, which requires a high dose of long-wave UVA. Consequently, exposure to UVB radiation functions to create melanin pigment, while UVA exposure ensures the oxidation of the pigment. Together, the proper combined UV exposure operates to create a light-protection mechanism.
As can be seen from FIGS. B1-B3, the relative strength of UVB is significantly diminished at wavelengths greater than approximately 305 nanonmeters.
Various types of glasses are used for tanning lamps. The two main glass types are “soft” glass and “hard” glass. In these cases, the terms “soft” and “hard” refer to the temperature needed to work them. “Hard” glasses contain relatively high percentages of silicon dioxide and/or aluminum or boric oxides. Fused quartz is a hard glass that is pure or almost pure silicon dioxide. Hard glasses can transmit a significant amount of UV radiation but are harder to work because of working temperatures that range from 1100 to 1600° C. Soft glass can be worked at a relatively low temperature (900° C.), and has a wide plastic range over which it can be worked. Fluorescent lamps, neon signs and most incandescent lamps used in the home are soft glass.
Typical soft glasses are soda-lime glass and lead glass. On example of a soda lime glass tubing is described as SG81 glass, which is a soda lime silicate. A product data sheet is attached hereto as FIG. A1.
Tanning lamps are made of a specially formulated soft glass that has much better transmission of ultraviolet (“UV”) in the UVA and UVB regions. A standard Osram Lime Glass is generally known to have a 50% UVB transmission characteristic at approximately 305 nanometers. One example of the formation of a UV absorbing lamp glass can be found in U.S. Pat. No. 5,350,972 to Bucher et. al., filed on May 25, 1993, the disclosure of which is incorporated herein by reference and made a part hereof.
It is an objective of the present invention to produce an ultraviolet transmitting lamp that provides enhanced transmission in the UVB range, and preferably in the range of approximately 283 to 305 nanometers.